1. Field of the Invention
This invention relates to devices operated by a plurality of intermittent fluid streams with particular application to a conveyor in which items are conveyed by spaced intermittent bursts of air.
2. Prior Art and Information Disclosure
Fluid streams of liquid or air are used in a number of diverse applications such as conveyors and irrigation systems.
For example, in application to conveyors, U.S. Pat. No. 5,031,643 to Hinz et al is for a pneumatic rotary conveyor for rod shaped articles disclosing a drum conveyor arranged to advance rod shaped objects (cigarettes) in a predetermined direction and an array of suction ports in the conveyor surface arranged to detachably secure the objects to the conveyor surface.
U.S. Pat. No. 4,981,206 to Franklin is for an apparatus for handling a package including a source of air that forces the package upward against a conveyor belt enabling the conveyor to transport the package.
Transport of integrated circuit devices (ICs) is an important operation in the manufacture and distribution of these devices. As a result of the huge quantity of ICs manufactured and tested throughout the world, the ICs are usually presented for testing by automatic handlers. The ICs are bulk stored in tubes or rails which are then emptied into the automatic handlers. Many of the more complex and expensive ICs are housed in ceramic packages with leads. After testing, the acceptable ICs are down loaded from the automatic handlers back into the tubes. Loading into tubes is done to facilitate movement of ICs from one operation to another.
When the ICs are loaded into the automatic handlers, frequently with a sloped gravitational feed, they collide with one another when they are stopped for the actual test operation. The collision oftentimes causes chipping of the edges of the ceramic packages. The chips are considered to be cosmetic (appearance) defects and cause the rejection (scrapping) of otherwise acceptable ICs. To minimize the occurrence of chipping, an operation called "singulation" (or slow down) is used to release the pans one at a time from the tubes. According to the present state of the art, singulation is performed by mechanical means such as with rollers or stop pins.
Valve bodies having a cylindrical cavity are disclosed for several applications. For example, U.S. Pat. No. 5,067,523 to Fraoli et al for a gas air controller unit discloses a valve body comprising a cylindrical chamber enclosing a hollow cylinder functioning as a mixing chamber. A source of gas and a source of air communicate with the mixing chamber through a respective opening in the chamber wall and cylinder when the openings are aligned by appropriate rotation of the hollow cylinder. The position of the cylinder and therefore the ratio of gas and air in the mixing chamber is controllable by a manually operated control knob coupled to the cylinder.
Drip irrigation for agricultural purposes is a process where control of a fluid stream is central to operation of the process. One of the problems in drip irrigation is to provide a uniform discharge of water from each nozzle located along the irrigation tube. As water flows continuously in the tube, pressure diminishes in proportion to the distance of the nozzle from the source of water so that rate of flow diminishes.